stack.push(FeatureExprFactory.True());
for (Stream lexer : lexers) {
Syntax s = lexer.scan();
while (s.kind() != Syntax.Kind.EOF) {
if (s.kind() == Syntax.Kind.CONDITIONAL) {
Syntax.Conditional c = s.toConditional();
if (c.tag() == Syntax.ConditionalTag.START)
stack.push(stack.peek().and(XtcPreprocessor.translate(c.presenceCondition())));
else if (c.tag() == Syntax.ConditionalTag.NEXT) {
stack.pop();
stack.push(stack.peek().and(XtcPreprocessor.translate(c.presenceCondition())));